1. Field of the Invention
The present invention relates to methods and compounds capable of decreasing hypoxia inducible factor (HIF) hydroxylase enzyme activity, thereby increasing the stability and/or activity of HIF. In particular, the compounds increase endogenous erythropoietin, ex vivo and in vivo.
2. State of the Art
Hypoxia inducible factor (HIF) is a basic helix-loop-helix (bHLH) PAS (Per/Arnt/Sim) transcriptional activator that mediates changes in gene expression in response to changes in cellular oxygen concentration. HIF is a heterodimer containing an oxygen-regulated α-subunit (HIFα), and a constitutively expressed β-subunit (HIFβ), also known as aryl hydrocarbon receptor nuclear transporter (ARNT). In oxygenated (normoxic) cells, HIFα subunits are rapidly degraded by a mechanism that involves ubiquitination by the von Hippel-Lindau tumor suppressor (pVHL) E3 ligase complex. Under hypoxic conditions, HIFα is not degraded, and an active HIFα/β complex accumulates in the nucleus, and activates the expression of several genes including glycolytic enzymes, glucose transporters, erythropoietin (EPO), and vascular endothelial growth factor (VEGF). (Jiang, et al., (1996) J. Biol. Chem., 271:17771-17778; Iliopoulus, et al., (1996) Proc. Natl. Acad. Sci. USA, 93:10595-10599; Maxwell, et al., (1999), Nature, 399:271-275; Sutter, et al., (2000) Proc. Natl. Acad. Sci. USA, 97:4748-4753; Cockman, et al., (2000) J. Biol. Chem., 275:25733-25741; and Tanimoto, et al., (2000) EMBO. J. 19:4298-4309.)
Levels of HIFα are elevated in most cells in response to hypoxia, and HIFα is induced in vivo when animals are subjected to anemia or hypoxia. HIFα levels rise within a few hours after the onset of hypoxia, and induce numerous beneficial cellular processes including cytoprotective effects, enhanced erythropoiesis, and physiological adaptation to ischemic or hypoxic states. Induction of HIFα is potentially beneficial in conditions such as myocardial acute ischemia and early infarction, pulmonary hypertension, inflammation, and anemia.
HIFα levels are also increased by a number of factors that mimic hypoxia, including iron chelators such as desferrioxamine (DFO), and divalent metal salts such as CoCl2. Additionally, compounds originally identified as inhibitors of procollagen prolyl hydroxylase enzymes have been found to stabilize HIFα. Examples of such compounds can be found, e.g., in Majamaa et al. (1984) Eur J Biochem 138:239-245; Majamaa et al. (1985) Biochem J 229:127-133; Kivirikko and Myllyharju (1998) Matrix Biot 16:357-368; Bickel et al. (1998) Hepatology 28:404-411; Friedman et al. (2000) Proc Natl Acad Sci USA 97:4736-4741; Franklin (1991) Biochem Soc Trans 19:812-815; and Franklin et al. (2001) Biochem J 353:333-338. Additionally, compounds that stabilize HIFα have been described in, e.g., International Publication Nos. WO 03/049686, WO 02/074981, WO 03/080566, WO 2004/108681, and WO 2006/094292.
There remains a need for compounds that are effective in the prevention of disorders associated with HIF, including anemia, and tissue damage caused by ischemia that occurs due to, e.g., atherosclerosis, diabetes, and pulmonary disorders such as pulmonary embolism, and the like. Thus, compounds that modulate HIF, which can be used to treat, and prevent HIF-associated disorders including conditions involving anemia, ischemia, and hypoxia, are provided herein.